The present research proposal involves the study of the cyclic AMP dependent protein kinase in the dog pancreas. Cyclic AMP has been implicated as a second messenger in the exocrine pancreas. Changes in pancreatic adenylate cyclase and cellular cyclic AMP have been reported during stimulation of fluid, bicarbonate, and enzyme secretion. The only presently known intracellular action of cyclic AMP is interaction with the protein kinase enzyme. Our aim is to investigate protein kinase activity under the influence of gastrointestinal hormones. The following hormones will be investigated: secretin, vasoactive intestinal polypeptide, cholecystokinin-pancreozymin and gastrin (pentagastrin). Hormonal effects will be studied both in vivo and in vitro. Protein kinase activity will be determined by measuring the incorporation of P32 from ATP- P32 into a receptor protein by the enzyme homogenate. The enzyme activity will be expressed as the ratio of activity without exogenous cyclic AMP to activity in presence of added cyclic AMP. It is hoped that the reported changes in cellular cyclic AMP under the influence of hormones, will also be detected in the protein kinase activity. It is believed that any results obtained from this study will increase out knowledge as to the mode of action of the gastrointestinal hormones in the exocrine pancreas.